Fujitsu developed the MAF3364, MAG3182, and MAG3091 as high-rpm versions (Allegro-5E and Allegro-5LE) of its 3.5-inch magnetic disk units (the Allegro-5 series) intended for high-end systems. These units, which began shipping in January 1999, featured giant magneto-resistive (GMR) heads with higher outputs than conventional MR heads.
The MAF3364, MAG3182, and MAG3091 had a maximum recording capacity of 36.4 GB thanks to the introduction of GMR heads and achieved a maximum internal data transfer speed of 44.7 MB per second (on the Ultra-2 SCSI interface), which was among the fastest at the time, thanks to a 10,000 rpm disk speed. The 7,200 rpm MAE3182 and MAE3091, which began shipping at the same time, offered recording capacities of 18.2 GB and 9.1 GB, respectively, in a one-inch profile.
Faster disk rotational speeds required heads that were both heat resistant and highly reliable. The GMR head, which used a newly developed heat-resistant anti-ferromagnetic material (a PtMn alloy), met both of these requirements. The six models in the MPD3XXXAT series of internal magnetic disk units for desktop computers, which came out at the same time, were also equipped with GMR heads, meaning GMR heads were used in all Fujitsu’s new models, even the previous year’s 2.5-inch units for notebook computers.